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Fig. 3

Amplitude and phase encoded signals. a Six different amplitude levels (depicted by the different colours) of a 500 ps optical pulse can be stored and retrieved after a storage time of 3.5 ns via direct detection. The amplitude of pulse 2 remains constant for the original and retrieved data pulse. The read-out efficiency of pulse 2 is lower due to practical limitations in the experiment (power limitation). The inset shows a zoom-in on the input amplitude levels and the readout amplitudes. b Simulation data of the amplitude response of the system. c Two phase levels of two 500 ps optical pulses, either 0 and π or π and 0 (depicted by the red and blue trace, respectively) are retrieved via homodyne detection after a storage time of 3.5 ns (orange and light blue trace). The insets show the two phases in phase space for the original (red/blue) and retrieved (orange/light blue) pulses. d Simulated phase response of the system (the colour schemes of the two encoded phases and the phase space diagram are according to the measurements depicted in c)